Embodiments of the present invention relate to rotors, for example in apparatus providing a source of power, such as in a hydrocarbon well facility.
In offshore oil and gas production control systems, much of the control equipment is installed on the seabed. This subsea equipment essentially opens and closes subsea valves that control and allow the flow of hydrocarbon fluid from the well. Electrical power and hydraulic power required for operating the equipment and valves installed on the seabed is normally provided by an electrical power unit and a hydraulic power unit installed topside, either on a rig, floating platform or onshore. The electrical power is carried to the subsea equipment via an umbilical cable which also includes a communication link (that carries control and instrumentation signals) together with hydraulic pipelines which carry hydraulic fluid for electrically actuated hydraulic fluid operated control valves.
The umbilical cable may be several kilometers long and is heavy and expensive so its design is therefore critical. The cost of the umbilical cable in a typical subsea production system has been estimated to be as much as 40% of the overall cost of the complete subsea system and a cost effective design is therefore essential. A reduction in the amount of electrical power to be transmitted subsea will reduce the size, rating and cost of the electrical cables required in the umbilical cable. Similarly, a reduction in the amount or pressure of hydraulic fluid in the hydraulic pipes in the umbilical cable will result in significant savings.